Sterilizing method and sterilizer

ABSTRACT

A sterilizing method for sterilizing a sterilization object housed in a chamber (11) includes a first vapor injection step (S104) of injecting vapor produced from a first aqueous solution of hydrogen peroxide to the inside of the chamber (11), an ozone injection step (S107) of injecting ozone gas to the inside of the chamber (11) after the first vapor injection step (S104), and a second vapor injection step (S109) of injecting vapor produced from pure water or vapor produced from a second aqueous solution of hydrogen peroxide to the inside of the chamber (11) after the ozone injection step (S107).

TECHNICAL FIELD

The present disclosure relates to a sterilizing method and a sterilizer.

BACKGROUND ART

Reusable medical instruments used for surgical operations and medicalcares in hospitals are subjected to treatment of sterilization aftersufficient cleaning in order to remove adhesive matter such as blood andprotein.

A sterilizing method is known that uses hydrogen peroxide as mainsterilization gas and further uses additional gas for executing suchsterilization treatment in order to improve the sterilizationefficiency. Patent Literature 1 discloses sterilizing method andapparatus that execute a series of steps of reducing a pressure in achamber housing an object to be sterilized, injecting vapor of anaqueous solution of hydrogen peroxide for sterilization to keep thestate, and further injecting ozone gas for sterilization to keep thestate.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent No. 5480975

SUMMARY OF THE INVENTION

The sterilizing method disclosed in Patent Literature 1 only keeps thesterilizing state after the injection of the ozone gas. The inventorshave confirmed through reproducibility tests that the sterilizationeffect is not particularly improved by the ozone gas. The sterilizingmethod and apparatus using plural kinds of sterilization gas thus stillneed to be improved in order to enhance the sterilization efficiency.

An object of the present disclosure is to provide a sterilizing methodand a sterilizer capable of improving a sterilization efficiency in theentire sterilizing treatment.

SOLUTION TO PROBLEM

A sterilizing method according to a first aspect of the presentdisclosure sterilizes a sterilization object housed in a chamber, themethod including a first vapor injection step of injecting vaporproduced from a first aqueous solution of hydrogen peroxide to an insideof the chamber, an ozone injection step of injecting ozone gas to theinside of the chamber after the first vapor injection step, and a secondvapor injection step of injecting vapor produced from pure water orvapor produced from a second aqueous solution of hydrogen peroxide tothe inside of the chamber after the ozone injection step.

A sterilizer according to a second aspect of the present disclosureincludes a chamber configured to house a sterilization object, anevaporator configured to communicate with the chamber and evaporate afirst aqueous solution of hydrogen peroxide, or a second aqueoussolution of hydrogen peroxide or pure water so as to be filledtherewith, an ozone generator configured to communicate with the chamberand produce ozone gas, and a controller configured to control anoperation of injecting, to an inside of the chamber, vapor produced bythe evaporator or the ozone gas produced by the ozone generator, whereinthe controller injects the ozone gas to the inside of the chamber afterinjecting the vapor produced from the first aqueous solution, andinjects the vapor produced from the pure water or the second aqueoussolution to the inside of the chamber after injecting the ozone gas soas to sterilize the sterilization object.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a sterilizeraccording to a first embodiment.

FIG. 2 is a flowchart showing a process of a sterilizing methodaccording to the first embodiment.

FIG. 3 is a table showing plural processing modes executed by thesterilizer according to the first embodiment.

FIG. 4 is a table showing various kinds of conditions used for asterilization treatment test according to the first embodiment.

FIG. 5 is a table showing results of the sterilization treatment testexecuted under the conditions shown in FIG. 4.

FIG. 6 is a graph showing a change in pressure inside a chamber in acase of Comparative Example 1.

FIG. 7 is a graph showing a change in pressure inside a chamber in acase of Comparative Example 2.

FIG. 8 is a graph showing a change in pressure inside a chamber in acase of Example.

FIG. 9 is a flowchart showing a process of a sterilizing methodaccording to a second embodiment.

FIG. 10 is a graph showing a change in pressure inside a chamber in acase of the second embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail belowwith reference to the drawings. The following dimensions, materials, andspecific numerical values described in the respective embodiments aredescribed for illustration purposes, and the present disclosure is notintended to be limited thereto unless otherwise specified. The elementshaving substantially the same functions and structures illustrated beloware designated by the same reference numerals, and overlappingexplanations are not made below. The elements described below but notrelated directly to the present disclosure are not shown in thedrawings.

First Embodiment

FIG. 1 is a schematic diagram showing a configuration of a sterilizer100 according to a first embodiment. The sterilizer 100 sterilizes anobject to be sterilize by use of sterilization gas. Materials mainlyincluded in the sterilization gas used in the present embodiment arehydrogen peroxide (H₂O₂) and ozone (O₃).

The object to be sterilized is herein presumed to be a medicalinstrument used in a hospital for surgical operations and medical caresand brought into contact with a blood circulatory system or aseptictissues. Examples of medical instruments include a heat-resistant steelproduct such as a pair of forceps, a surgical tweezer, and surgicalscissors, and a non-heat resistant resin product such as a hardendoscope made of stainless steel used for laparoscopic surgery, a softendoscope used for bronchial or urinary surgery, and a power supplycable as an attachment for these endoscopes. The object to be sterilizedis herein presumed to be housed in a chamber 11 of the sterilizer 100 ina state of being preliminarily put in a sterilization bag orpreliminarily wrapped with a sterilization wrap. The sterilization bagor the sterilization wrap is nonwoven fabric mainly including resinmaterial such as polyethylene and is fine mesh, so as to allow thesterilization gas to pass therethrough but block bacteria.

The sterilizer 100 includes a chamber unit 10, a hydrogen peroxidesupply unit 20, an ozone supply unit 30, an exhaustion unit 40, an airintroduction unit 50, and a control unit 60.

The chamber unit 10 includes the chamber 11 for housing the object to besterilized, and peripheral components. The chamber unit 10 includes thechamber 11 having a door 12, a first heater 13, and a first manometer14.

The chamber 11 is a holder for housing and placing the object to besterilized therein. The chamber 11 is referred to also as asterilization container. The chamber 11 is made of stainless steel or analuminum alloy, and has a structure resistant to a vacuum anddecompression. The present embodiment is illustrated below with a casein which a capacity of the chamber 11 is 100 liters (L), for example.The door 12 is arranged on the chamber 11 in an openable manner. Thechamber 11 is tightly sealed to prevent vacuum leakage or leakage of thesterilization gas when the door 12 is closed so that the inside of thechamber 11 is decompressed.

The first heater 13 is installed at a circumference of the chamber 11together with a thermal material to keep the internal temperature of thechamber 11 constant during the sterilization treatment. The temperatureof the chamber 11 is measured by a thermometer (not illustrated)arranged at the chamber 11.

The first manometer 14 is a vacuum gauge arranged at the chamber 11 tomeasure the pressure inside the chamber 11.

The hydrogen peroxide supply unit 20 supplies vapor of hydrogen peroxideto the chamber 11 during the sterilization treatment. The hydrogenperoxide supply unit 20 according to the present embodiment canindependently supply the vapor separately produced from two aqueoussolutions of hydrogen peroxide. One of the aqueous solutions of hydrogenperoxide is referred to below as a “first aqueous solution”, and theother aqueous solution of hydrogen peroxide is referred to below as a“second aqueous solution”. A concentration of the hydrogen peroxidecontained in the first aqueous solution and a concentration of thehydrogen peroxide contained in the second aqueous solution aredetermined according to the presence or absence of a duct part in theobject to be sterilized or the material used for the object to besterilized, as described below. The hydrogen peroxide supply unit 20includes a bottle 21, an extraction pipe 22, a tube pump 23, a storagepart 24, an evaporator 26, and a second heater 29.

The bottle 21 houses the aqueous solution of the hydrogen peroxide. Thebottle 21, when disposable, is referred to also as a cartridge. Thepresent embodiment uses the two aqueous solutions of the hydrogenperoxide, and uses a first bottle 21 a for housing the first aqueoussolution and a second bottle 21 b for housing the second aqueoussolution.

The extraction pipe 22 extracts the aqueous solutions of the hydrogenperoxide from the respective bottles 21, and supplies the extractedaqueous solutions to the storage part 24. The present embodiment uses afirst extraction pipe 22 a that extracts the first aqueous solution fromthe first bottle 21 a, and a second extraction pipe 22 b that extractsthe second aqueous solution from the second bottle 21 b.

The tube pump 23 is arranged in the middle of the respective extractionpipes 22 to suck an appropriate amount of the aqueous solutions of thehydrogen peroxide every time out of the respective bottles 21. Thepresent embodiment uses a first tube pump 23 a arranged in the middle ofthe first extraction pipe 22 a, and a second tube pump 23 b arranged inthe middle of the second extraction pipe 22 b. The respective extractionpipes 22 may be provided with an optical liquid level sensor (notillustrated), for example. The respective tube pumps 23 suck up theaqueous solutions of the hydrogen peroxide until the liquid level sensorresponds, and temporarily stop upon the response of the liquid levelsensor and then rotate with a predetermined number of times, so as tosupply the predetermined amount of the respective aqueous solutions tothe storage part 24.

The storage part 24 is connected to the respective extraction pipes 22to temporarily store the predetermined amount of the respective aqueoussolutions of the hydrogen peroxide sucked out of the bottles 21 beforethe supply to the evaporator 26. The storage part 24 used may be asemi-transparent fluororesin tube through which the amount of thesolution stored inside can be visually confirmed. Since the respectivetube pumps 23 can supply the constant amount of the solution stably whendriven under an atmospheric pressure, the storage part 24 may besupplied with the air via a first filter 25 so as to be under theatmospheric pressure. The first filter 25 is a high-efficiencyparticulate air (HEPA) filter, for example.

The evaporator 26 communicates with the storage part 24 via a firstsupply pipe 27, and evaporates the aqueous solution of the hydrogenperoxide introduced through the storage part 24. The evaporator 26 is,for example, made of stainless steel so as to have resistance tocorrosion caused by the hydrogen peroxide, and has a structure resistantto a vacuum and decompression since the evaporator 26 is decompressedsimultaneously with the chamber 11.

The first supply pipe 27 is provided with a first electromagnetic valve70. When the first electromagnetic valve 70 is open, the aqueoussolution of the hydrogen peroxide stored in the storage part 24 issucked and introduced toward the decompressed evaporator 26. Since thestorage part 24 is under the atmospheric pressure after being suppliedwith the air via the first filter 25, the air is also sucked togetherwith the aqueous solution of the hydrogen peroxide. The aqueous solutionof the hydrogen peroxide remaining in the storage part 24 and the firstsupply pipe 27 is also sucked and introduced toward the evaporator 26,so that the constant amount of the vapor of the hydrogen peroxide isstably supplied to the inside of the chamber 11.

The evaporator 26 communicates with the chamber 11 via a plurality ofinjection pipes 28. The present embodiment uses a first injection pipe28 a and a second injection pipe 28 b arranged on a ceiling at twopositions in the diagonal line. The first injection pipe 28 a isprovided with a second electromagnetic valve 71, and the secondinjection pipe 28 b is provided with a third electromagnetic valve 72.When the aqueous solution of the hydrogen peroxide is evaporated in theevaporator 26 to increase the pressure inside the evaporator 26, thesecond electromagnetic valve 71 or the third electromagnetic valve 72 isopened for a predetermined period of time, so that the vapor of theaqueous solution of the hydrogen peroxide is injected to the inside ofthe chamber 11. The arrangement of the plural injection pipes 28 asdescribed above can further enhance the uniform diffusion of the vaporinside the chamber 11. The evaporator 26 may be provided with a pressuresensor 39 for determining whether the pressure inside the evaporator 26is increased to a level within a predetermined range after the injectionof the vapor so as to determine whether the predetermined amount of thevapor is supplied from the storage part 24.

The second heater 29 is arranged at a circumference of the evaporator 26to keep the internal temperature of the evaporator 26 constant. Theinside of the evaporator 26 is constantly kept at a predeterminedtemperature in a range of 65° C. to 120° C., for example.

The ozone supply unit 30 supplies the ozone gas to the chamber 11 duringthe sterilization treatment. The ozone gas used in the presentembodiment is produced inside the ozone supply unit 30. The ozone supplyunit 30 includes an oxygen generation device 31, an ozone generator 32,an ozone densitometer 33, a buffer tank 34, and a second manometer 35.

The oxygen generation device 31 produces oxygen (O₂) serving as rawmaterial of ozone. The oxygen generation device 31 can adopt a pressureswing adsorption (PSA) mode that causes nitrogen in the air to beadsorbed to an adsorbent such as zeolite to produce oxygen with a highconcentration. In particular, the oxygen generation device 31 may be aPSA device having a discharge pressure in a range of about 0.03 to 0.08MPa as a gauge pressure, and a flowing amount in a range of about 1 to 4L/min A pipe connecting the oxygen generation device 31 and the ozonegenerator 32 is provided with a fourth electromagnetic valve 73.Controlling the open and closed states of the fourth electromagneticvalve 73 as appropriate can regulate the supply amount of the oxygen tothe ozone generator 32.

The ozone generator 32 produces the ozone gas from the oxygen producedby the oxygen generation device 31. The ozone generator 32 can adopt asilent discharge mode that applies a high voltage with a high frequencyto the oxygen to be discharged and decomposed so as to produce theozone. The present embodiment is illustrated with a case in which theozone supply unit 30 includes two ozone generators 32. A productionability of the ozone generators 32 is given by 2 g/hr×two ozonegenerators=4 g/hr, for example. The ozone generators 32 in this caseoperate for 1.5 minutes while receiving 1 L/min of the oxygen, so as toproduce the ozone with the amount given by 4 g×1.5 minutes/60minutes=0.1 g. The ozone generators 32 communicate with the buffer tank34 via a second supply pipe 36.

The ozone densitometer 33 measures a concentration of the ozone gasproduced by the ozone generators 32 in the second supply pipe 36. Forexample, a case is presumed in which a measurement value obtained by theozone densitometer 33 is 70 g/m³ when the ozone gas is allowed to flowthrough the second supply pipe 36 for 1.5 minutes with the flowingamount of 1 L/min. The amount of the ozone produced in this casecorresponds to the amount given by 1 L/min×1.5 minutes×70 g/1000 L=0.105g. In addition, a case is presumed in which 0.105 g of the ozone gas isinjected to the inside of the chamber 11 with the capacity of 100 L, andthe air is further introduced thereto so as to be under the atmosphericpressure. The concentration of the ozone in the chamber 11 in this casecorresponds to a volume concentration given by 0.105 g/48 g×22.4 L/100L×1,000,000=490 ppm, where 48 g is a molecular amount of the ozone, and22.4 L is the amount of reference gas.

The second supply pipe 36 is provided with a fifth electromagnetic valve74 between the ozone densitometer 33 and the buffer tank 34. The secondsupply pipe 36 between the ozone densitometer 33 and the fifthelectromagnetic valve 74 may communicate with the exhaustion unit 40 viaa piping system X including a sixth electromagnetic valve 75. When thefifth electromagnetic valve 74 is closed and the sixth electromagneticvalve 75 is open, the ozone gas flowing from the respective ozonegenerators 32 is supplied toward the exhaustion unit 40.

The buffer tank 34 temporarily stores the ozone gas produced by therespective ozone generators 32 before the supply to the evaporator 26.The buffer tank 34 is, for example, made of stainless steel so as tohave resistance to corrosion caused by the hydrogen peroxide, and has astructure resistant to decompression. The present embodiment isillustrated below with a case in which a capacity of the buffer tank 34is two liters (L). The buffer tank 34 communicates with the evaporator26 via a third supply pipe 37. The third supply pipe 37 is provided witha seventh electromagnetic valve 76. When the ozone gas is injected tothe buffer tank 34 while the seventh electromagnetic valve 76 is closed,the pressure inside the buffer tank 34 is transiently increased.

The second manometer 35 is a vacuum gauge arranged at the buffer tank 34to measure the pressure inside the buffer tank 34. A controller 61monitors the pressure inside the buffer tank 34 by use of the secondmanometer 35, so as to confirm whether the ozone injected is increasedto a predetermined pressure in the buffer tank 34, or confirm whetherleakage or stoppage of the ozone is caused in the second supply pipe 36or the like.

According to the present embodiment, the ozone gas supplied from thebuffer tank 34 is not directly but indirectly injected to the chamber 11via the evaporator 26. An introduction port of the sterilization gastoward the chamber 11 is shared with the hydrogen peroxide and the ozonegas.

As another embodiment, the ozone gas may be directly injected to thechamber 11 from the buffer tank 34 without bypassing the evaporator 26.The direct injection of the ozone gas to the chamber 11 withoutbypassing the evaporator 26 has the advantage of increasing the speed ofdiffusion of the ozone gas inside the chamber 11. This case also has theadvantage of increasing the ozone concentration in the chamber 11 whenthe second electromagnetic valve 71 and the third electric valve 72arranged between the evaporator 26 and the chamber 11 are closed.

The exhaustion unit 40 vents the atmosphere inside the chamber 11 so asto decompress the inside of the chamber 11 or discharge the gas presentinside the chamber 11 to the outside. In particular, the exhaustion unit40 removes excessive gas from the chamber 11 or the object to besterilized itself to decompress the inside of the chamber 11 to a mediumvacuum level of 100 Pa or below, for example, before the sterilizationtreatment in order to improve the sterilization effect during thesterilization treatment. The exhaustion unit 40 also eliminates thesterilization gas remaining in the chamber 11 or the object to besterilized after the sterilization treatment. The exhaustion unit 40includes a vacuum pump 41, a catalyst tank, and a heater.

The vacuum pump 41 used can be a dry pump such as a scroll pump formedium vacuum, or a hydraulic rotating pump such as a rotary pump. Thevacuum pump 41 in the present embodiment is a hydraulic rotating pump.The vacuum pump 41 and the chamber 11 communicate with each other via anexhaustion pipe 38. The exhaustion pipe 38 is provided with an eighthelectromagnetic valve 77. When the pressure inside the chamber 11reaches a predetermined value during the decompression, for example, thecontroller 61 closes the eighth electromagnetic valve 77 to stop theoperation of the vacuum pump 41.

The catalyst tank is made of stainless steel, for example, and includesa catalyst such as a pellet type and a honeycomb type. The catalystmainly includes manganese dioxide, for example, and decomposes thehydrogen peroxide and the ozone. The catalyst tank in the presentembodiment is arranged at two positions on the upstream side and thedownstream side of the vacuum pump 41 in view of decomposing gas havinga risk of corroding the vacuum pump, and also keeping the exhaustionspeed as appropriate. A first catalyst tank 42 is a catalyst tankarranged on the upstream side of the vacuum pump 41. A second catalysttank 43 is a catalyst tank arranged on the downstream side of the vacuumpump 41.

As described above, the ozone supply unit 30 can supply the ozone gas tothe exhaustion unit 40 via the piping system X such that the ozonegenerators 32, the fifth electromagnetic valve 74, and the sixthelectromagnetic valve 75 are controlled as appropriate.

The heater keeps the respective catalyst tanks at a temperature in arange of 60° C. to 90° C., for example. A third heater 44 keeps thetemperature of the first catalyst tank 42. A fourth heater 45 keeps thetemperature of the second catalyst tank 43.

The air introduction unit 50 introduces the air into the inside of thechamber 11. The air introduction unit 50 includes a second filter 51 anda plurality of introduction ports.

The second filter 51 prevents dust in the air from entering the insideof the chamber 11 upon the introduction of the air. The second filter 51used may be a HEPA filter which is a nonwoven filter of fine mesh, forexample.

The respective introduction ports introduce the air through the secondfilter 51 to the inside of the chamber 11. The introduction ports arepreferably arranged at different positions from each other in thechamber 11 in order to equalize the gas concentration inside the chamber11 simultaneously with the introduction of the air. The presentembodiment uses two introduction ports, a first introduction port 52 anda second introduction port 53, for example, arranged on the ceiling attwo positions in the diagonal line. The first introduction port 52 isprovided with a ninth electromagnetic valve 78. The second introductionport 53 is provided with a tenth electromagnetic valve 79. Thecontroller 61 independently controls the open and closed states of theninth electromagnetic valve 78 and the tenth electromagnetic valve 79,so as to introduce the air into the inside of the chamber 11 from thedifferent positions at an appropriate timing.

The introduction ports are not limited to those directly arranged at thechamber 11. As another embodiment, the introduction ports may beconnected to the chamber 11 via the evaporator 26, or the introductionports may be connected to the chamber 11 via the buffer tank 34. Theintroduction ports may also be connected to the chamber 11 via both theevaporator 26 and the buffer tank 34, for example.

The control unit 60 controls the driving operations of power systemelements in the respective units included in the sterilizer 100 inaccordance with various kinds of operating commands The control unit 60includes the controller 61 and a touch panel 62. The controller 61 iselectrically connected to the respective power system elements andmeasurement system elements, for example. The controller 61 controls theoperations of the respective power system elements in accordance with acommand input via the touch panel 62, a sequence of control operationspreliminarily stored, or a detection signal acquired from various typesof sensors. The touch panel 62 is electrically connected to thecontroller 61, and is used by the operator to input the information orcommand and to visually recognize the information provided from thesterilizer side.

Next, a process of a sterilizing method according to the presentembodiment by use of the sterilizer 100 is described below.

FIG. 2 is a flowchart showing the process of the sterilizing methodaccording to the present embodiment. The sterilizing treatment by thesterilizing method according to the present embodiment is mainly dividedinto three steps. The first step is a pretreatment step including atreatment mode selection step S101. The second step includessterilization steps from a first decompression step S102 to a secondstate-keeping step S111. The last third step is an aeration step S113.

Before starting the treatment mode selection step S100, the operatorsuch as a nurse in a hospital places the object to be sterilized in thechamber 11, and closes the door 12 to make the inside of the chamber 11airtight. At this point, the power of the sterilizer 100 is presumed tobe already turned on so as to complete a warming-up.

In the sterilization treatment in the present embodiment, the operatorcan choose a treatment mode depending on the type of the object to besterilized. The type of the object to be sterilized is classifiedaccording to the shape and the material of the object to be sterilized,for example. In particular, the shape of the object to be sterilized maybe classified in accordance with the presence or absence of a duct part.The treatment mode selection step S101 is a step of inputting thetreatment mode chosen by the operator to the sterilizer 100.

FIG. 3 is a table showing the respective treatment modes executable bythe sterilizer 100. The treatment modes may include the following threemodes, for example. A short mode is applied to a case in which theobject to be sterilized is a medical instrument having no duct part. Themedical instrument of this type is a steel product such as a pair offorceps, for example, and is mainly subjected to surface sterilization.A normal mode is applied to a case in which the object to be sterilizedis a medical instrument made of resin having a duct part. A long mode isapplied to a case in which the object to be sterilized is a medicalinstrument made of stainless steel having a duct part. The medicalinstrument of this type is a hard endoscope having a thin tube with aninner diameter of about 1 mm, for example.

The treatment modes differ from each other in the treatment time, theinjected amount of the aqueous solution of the hydrogen peroxide, or thenumber of exposure times in the following steps. The column of theinjected amount of the aqueous solution of the hydrogen peroxide in thetable shown in FIG. 3 indicates a range of possible values per pulsecorresponding to one operation in the series of the sterilization steps.In particular, the upper row in the column indicates the algebraregarding the injected amount of the first aqueous solution, and thelower row indicates the algebra regarding the injected amount of thesecond aqueous solution.

The sterilization steps according to the present embodiment include afirst decompression step S102, a first vapor preparation step S103, afirst vapor injection step S104, and a first state-keeping step S105.

The first decompression step S102 is a step of decompressing the insideof the chamber 11 to a predetermined vacuum degree to dischargeexcessive gas contained in the object to be sterilized. The controller61 opens the eighth electromagnetic valve 77 after driving the vacuumpump 41 so as to decompress the inside of the chamber 11. The controller61 further opens the second electromagnetic value 71, the thirdelectromagnetic value 72, and the seventh electromagnetic value 76, soas to decompress the inside of each of the evaporator 26 and the buffertank 34, in addition to the chamber 11. The treatment time indicated inthe table shown in FIG. 3 is measured from the point of starting thedecompression in this case. A target pressure in the first decompressionstep S102 is set to 50 Pa or lower. The controller 61, when the pressurereaches the target pressure, closes the second electromagnetic valve 71,the third electromagnetic valve 72, the seventh electromagnetic valve76, and the eighth electromagnetic valve 77 to stop the vacuum pump 41.The controller 61 then leads the process to proceed to the first vaporpreparation step S103 after the first decompression step S102.

When the treatment mode is the long mode, the object to be sterilized isa thin tube made of stainless steel, for example. Upon the choice of thelong mode, the temperature of the object to be sterilized may bepreliminarily increased and kept for a predetermined period of time suchas about two minutes while keeping the state of the pressure reached, soas to reduce an influence of water condensation inside the duct part asmuch as possible.

The first vapor preparation step S103 is a step of producing the vaporof the first aqueous solution to be injected in the following firstvapor injection step S104. The controller 61 first rotates the firsttube pump 23 a to suck the first aqueous solution from the first bottle21 a, and then injects an equally-divided amount of the defined amountof the first aqueous solution to the storage part 24. The defined amountis a total injected amount per pulse, and differs from the respectivetreatment modes as shown in FIG. 3. For example, when the treatment modeis the short mode, the concentration of the hydrogen peroxide containedin the first aqueous solution is set to a predetermined concentration(x1) in a range of 30% to 60%, and the defined amount is a predeterminedamount (y1) in a range of 1 to 4 ml. When the defined amount is dividedby two and is then injected, for example, the equally-divided amount ofthe defined amount is half of y1, which is a predetermined amount (y1/2)in a range of 0.5 to 2 ml. The controller 61 then opens the firstelectromagnetic valve 70 for a predetermined period of time such as fiveseconds. Since the inside of the evaporator 26 has been alreadydecompressed, the first aqueous solution is immediately sucked up to theevaporator 26. The air then enters the storage part 24, whichcommunicates with the atmosphere, via the first filter 25 so that thefirst aqueous solution remaining in the storage part 24 or the firstsupply pipe 27 is also sent to the evaporator 26. The controller 61 thencloses the first electromagnetic valve 70 to evaporate the first aqueoussolution in the evaporator 26 for a predetermined period of time such asfive seconds. The evaporator 26 is constantly kept at a predeterminedtemperature in a range of 65° C. to 120° C., for example. When aregulated amount of the first aqueous solution is injected so as to besubstantially completely evaporated inside the evaporator 26 with apredetermined value within a capacity in a range of 0.5 to 2 L under apressure of 50 Pa, for example, the pressure is presumed to be increasedto a level of about a saturated vapor pressure. The controller 61 thenleads the process to proceed to the first vapor injection step S104after the first vapor preparation step S103.

The first vapor injection step S104 is a step of injecting the vapor ofthe first aqueous solution produced by the evaporator 26 to the insideof the chamber 11. The controller 61 first opens the secondelectromagnetic valve 71 and the third electromagnetic valve 72 for apredetermined period of time such as ten seconds. The vapor of the firstaqueous solution is then strongly injected to the inside of the chamber11 due to the difference in the pressure. When the object to besterilized particularly has a duct part, the vapor penetrates the insideof the duct part more easily as the difference in the pressure ishigher. In addition, the vapor is easily equalized inside the chamber 11as described above. The controller 61 then closes the secondelectromagnetic valve 71 and the third electromagnetic valve 72. Thecontroller 61 repeats the injection of the vapor of the first aqueoussolution in the same process in accordance with the respective treatmentmodes. For example, when the treatment mode is the short mode, the vaporof the first aqueous solution is to be injected to the evaporator 26 perpulse with the amount corresponding to the predetermined concentration(x1) in the range of 30% to 60% which is multiplied by the predeterminedamount (y1) in the range of 1 to 4 ml. If a large amount of the firstaqueous solution is injected at once, the inside of the evaporator 26reaches the saturated vapor pressure, which may impede the sufficientevaporation to cause the first aqueous solution to remain in theevaporator 26. In view of this, the controller 61 may divide the amountof the first aqueous solution by two so as to evaporate and sequentiallyinject the second aqueous solution half-and-half to the chamber 11. Thecontroller 61 may divide the amount of the first aqueous solution intomore than two so as to sequentially inject the vapor of the firstaqueous solution to the chamber 11. The controller 61 then leads theprocess to proceed to the first state-keeping step S105 after the firstvapor injection step S104.

The first state-keeping step S105 is a step of keeping the vapor of thefirst aqueous solution in the chamber 11 for a predetermined period oftime to sterilize the object to be sterilized. The keeping time in therespective treatment modes in this case differs from each other. Thekeeping time in the short mode is three minutes, for example. Thekeeping time in the normal mode is four minutes, for example. Thekeeping time in the long mode is six minutes, for example. The keepingtime gradually increases in the order of the short mode, the normalmode, and the long mode.

The sterilization steps also include an ozone preparation step S106 andan ozone injection step S107.

The ozone preparation step S106 is a step of producing the ozone gas tobe injected in the following ozone injection step S107. The ozonepreparation step S106 is not necessarily executed after the completionof the first state-keeping step S105, but is only required to beexecuted before the start of the ozone injection step S107 so as toprepare the ozone gas. The controller 61 first opens the fourthelectromagnetic valve 73 to supply the oxygen with a concentration of95%, for example, to the ozone generators 32. The controller 61 mayclose the fifth electromagnetic valve 74 and open the sixthelectromagnetic valve 75 for several tens of seconds from the start ofdriving the ozone generators 32, so as to lead the ozone gas to flowthrough the piping system of the first catalyst tank 42 withoutsupplying the ozone gas to the buffer tank 34 until the concentrationsof the oxygen and the ozone are stable. The controller 61 then closesthe sixth electromagnetic valve 75 and opens the fifth electromagneticvalve 74, so as to fill the buffer tank 34 with the ozone gas untilreaching a predetermined flowing amount, a predetermined concentration,and a predetermined period of time. The controller 61 after finishingfilling the buffer tank 34 with the ozone gas closes the fifthelectromagnetic valve 74 to stop driving the ozone generators 32.

The ozone injection step S107 is a step of injecting the ozone gasproduced in the ozone preparation step S106 to the chamber 11. The ozoneinjection step S107 is executed after the completion of the firststate-keeping step S105. The controller 61 opens the seventhelectromagnetic valve 76 and further opens the second electromagneticvalve 71 and the third electromagnetic valve 72 for a predeterminedperiod of time such as five seconds to inject the ozone gas to thechamber 11. The pressure inside the buffer tank 34 is set to apredetermined pressure in a range of about 0.03 to 0.08 MPa to themaximum as a gauge pressure, or a predetermined pressure in a range ofabout 0.13 to 0.18 MPa as an absolute pressure. The injection of theozone gas to the inside of the chamber 11 under the decompression of3000 Pa or less as an absolute pressure is presumed to be completedwithin about several seconds due to the pressure difference. Thesterilizer 100 thus can allow the ozone with the small amount to beefficiently injected to the chamber 11 due to the use of the buffer tank34 so as to contribute to the sterilization.

The sterilization steps further include a second vapor preparation stepS108, a second vapor injection step S109, an outside air injection stepS110, and a second state-keeping step S111.

The second vapor preparation step S108 is a step of producing the vaporof the second aqueous solution to be injected in the following secondvapor injection step S109. The second vapor preparation step S108 is notnecessarily executed after the completion of the ozone injection stepS107, but is only required to be executed before the start of the secondvapor injection step S109 so as to prepare the vapor of the secondaqueous solution. The generation of the vapor of the second aqueoussolution may be executed through a process similar to the generation ofthe vapor of the first aqueous solution in the first vapor preparationstep S103.

The controller 61 first rotates the second tube pump 23 b to suck thesecond aqueous solution from the second bottle 21 b, and then injects anequally-divided amount of the defined amount to the storage part 24. Forexample, when the treatment mode is the short mode, the concentration ofthe hydrogen peroxide contained in the second aqueous solution is set toa predetermined concentration (x2) in a range of 0.1% to 10%, and thedefined amount is a predetermined amount (y2) in a range of 2 to 8 ml.When the defined amount is divided by two and is then injected, forexample, the equally-divided amount of the defined amount is half of y2,which is a predetermined amount (y2/2) in a range of 1 to 4 ml. Thecontroller 61 then opens the first electromagnetic valve 70 for apredetermined period of time such as five seconds. Since the inside ofthe evaporator 26 has been already decompressed, the second aqueoussolution is immediately sucked up to the evaporator 26. The air thenenters the storage part 24, which communicates with the atmosphere, viathe first filter 25 so that the second aqueous solution remaining in thestorage part 24 or the first supply pipe 27 is also sent to theevaporator 26. The controller 61 then closes the first electromagneticvalve 70 to evaporate the second aqueous solution in the evaporator 26for a predetermined period of time such as five seconds. The evaporator26 is constantly kept at a predetermined temperature in a range of 65°C. to 120° C., for example. When a regulated amount of the secondaqueous solution is injected so as to be substantially completelyevaporated inside the evaporator 26 with a predetermined value within acapacity in a range of 0.5 to 2 L under a pressure of 50 Pa, forexample, the pressure is presumed to be increased to a level of about asaturated vapor pressure. The controller 61 then leads the process toproceed to the second vapor injection step S109 after the second vaporpreparation step S108.

The second vapor injection step S109 is a step of injecting the vapor ofthe second aqueous solution produced by the evaporator 26 to the insideof the chamber 11. The ozone gas itself cannot contribute to thesterilization well, but increases the reactivity when moisture is addedthereto. The reason for this is presumed that a OH radical or the likeis produced when the ozone reacts with moisture or the remaininghydrogen peroxide on surfaces of bacteria so as to effectively destroycell walls of the bacteria. In view of this, the present embodimentinjects the vapor of the second aqueous solution to the inside of thechamber 11 immediately after the completion of the injection of theozone gas. The hydrogen peroxide contained in the vapor injected to theinside of the chamber 11 is presumed to penetrate cells of the bacteriathrough the cell walls destroyed by the ozone to attack cell nuclei, soas to improve the sterilization effect.

The sterilization effect is increased as the concentration of thehydrogen peroxide contained in the second aqueous solution is higher.The increase in the concentration of the hydrogen peroxide contained inthe second aqueous solution can be presumed to lead to a reduction inthe treatment time. The present embodiment is illustrated with a case,when the treatment mode is the long mode, in which the concentration ofthe hydrogen peroxide contained in the second aqueous solution is set tothe predetermined concentration (x1) in the range of 30% to 60% that isequal to the concentration of the hydrogen peroxide contained in thefirst aqueous solution. While the injected amount per pulse in the shortmode or the normal mode is set to the predetermined value (y2) in therange of 2 to 8 ml, the injected amount in the long mode can be set to asmaller predetermined amount (y3) in a range of 1 to 5 ml.

As described above, the second vapor injection step S109 is executedimmediately after the completion of the ozone injection step S107. Theinjection of the vapor of the second aqueous solution may be executedthrough a process similar to the injection of the vapor of the firstaqueous solution in the first vapor injection step S104.

The controller 61 first opens the second electromagnetic valve 71 andthe third electromagnetic valve 72 for a predetermined period of timesuch as ten seconds, and injects the vapor of the second aqueoussolution to the chamber 11. The controller 61 then closes the secondelectromagnetic valve 71 and the third electromagnetic valve 72. Thecontroller 61 repeats the injection of the vapor of the second aqueoussolution in the same process in accordance with the respective treatmentmodes. When the treatment mode is the short mode, the controller 61 inthis case may also divide the amount of the second aqueous solution ofy2 (2 to 8 ml) by two so as to evaporate and sequentially inject thesecond aqueous solution half-and-half to the chamber 11, for example.The controller 61 may divide the amount of the second aqueous solutioninto more than two so as to sequentially inject the vapor of the secondaqueous solution to the chamber 11. The controller 61 then leads theprocess to proceed to the outside air injection step S110 after thesecond vapor injection step S109.

While the present embodiment is illustrated above with the case ofinjecting the vapor of the second aqueous solution of the hydrogenperoxide in the second vapor injection step S109, the method may injectthe vapor of pure water such as purified water to which sterilization ordisinfection treatment is subjected, instead of the second aqueoussolution. In this case, the pure water is stored in the second bottle 21b. The pure water is then evaporated by the evaporator 26. The use ofthe pure water instead of the second aqueous solution can also have theadvantage of improving the reactivity of the ozone gas, as in the casedescribed above. The table shown in FIG. 3 illustrates the case in whichthe concentration of the hydrogen peroxide contained in the secondaqueous solution in the short mode and the normal mode (x2: apredetermined value in a range of 0.1% to 10%) is greatly lower than theconcentration of the hydrogen peroxide contained in the first aqueoussolution (x1: a predetermined value in a range of 30% to 60%). In thecase in which one of these two treatment modes can be chosen and thesterilization effect is not strictly required for the object to besterilized, for example, the pure water can be used instead of thesecond aqueous solution. This can decrease the used amount of thehydrogen peroxide in the entire sterilization treatment.

In the outside air injection step S110 is a step of injecting theoutside air that is the atmosphere or dry nitrogen gas to the inside ofthe chamber 11. The present embodiment is illustrated below with a casein which the outside air is the atmosphere. The outside air injectionstep S110 is executed immediately after the completion of the secondvapor injection step S109. The injection of the atmosphere to the insideof the chamber 11 pushes the hydrogen peroxide or the ozone gascongested particularly in the middle of the duct part in the object tobe sterilized, so as to further promote the sterilization. The injectionof the atmosphere to the inside of the chamber 11 also equalizes thedistribution of the concentration of the gas present inside the chamber11 so as to ensure the uniform sterilization. The injection of theatmosphere to the inside of the chamber 11 further increases theinternal pressure to lead the hydrogen peroxide in the vapor to beslightly condensed on the surface of the object to be sterilized, so asto improve the sterilization effect. The condensation as used herein isreferred to also as micro-condensation.

The controller 61 injects the air to the inside of the chamber 11 viathe air introduction unit 50. In particular, the controller 61 controlsthe open and closed states of the ninth electromagnetic valve 78 and thetenth electromagnetic valve 79 as appropriate, so as to regulate theinjected amount of the air introduced through the second filter 51. Theair is continuously introduced until reaching a predetermined pressure.In the present embodiment, the controller 61 closes the ninthelectromagnetic valve 78 and the tenth electromagnetic valve 79 afterinjecting the air until the pressure inside the chamber 11 reaches about90 kPa that is about 90% of the atmospheric pressure. The reason forthis is that the gas may leak out of the door 12 through the sealingpart if the internal pressure of the chamber 11 is equal to the externalpressure. The controller 61 then leads the process to proceed to thesecond state-keeping step S111 after the outside air injection stepS110.

As described above, the outside air injection step S110 is effectiveparticularly upon choosing the normal mode or the long mode that isapplied to the case in which the object to be sterilized has a ductpart. In the case of the short mode for mainly executing the surfacesterilization on the object to be sterilized not having a duct part, theoutside air injection step S110 is not necessarily executed in view ofthe simplification of the step when the short mode can ensure thepreferable sterilization effect.

The second state-keeping step S111 is a step of keeping the state of theinside of the chamber 11 for a predetermined period of time after thecompletion of the outside air injection step S110. Keeping the state ofthe inside of the chamber 11 for the predetermined period of time canfurther promote the sterilization action as described in the outside airinjection step S110. The keeping time in the respective treatment modesas used herein differs from each other. The keeping time in the shortmode is two minutes, for example. The keeping time in the normal mode isthree minutes, for example. The keeping time in the long mode is fiveminutes, for example.

The sterilization steps as described above may be repeated several timesas necessary depending on the object to be sterilized. The controller 61then determines whether the operation of the series of the sterilizationsteps needs to be repeated (step S112) after the completion of thesecond state-keeping step S111. The first operation of the sterilizationsteps is counted as one as the number of the exposure times, and thenumber of the exposure times in the following operations is indicated bythe pulse number. The controller 61, when determining that the operationof the sterilization steps needs to be repeated (YES), leads the processto proceed to the first decompression step S102 so as to execute thesterilization step for the second pulse. When determining that no moreoperation of the sterilization steps is needed (NO), the controller 61leads the process to proceed to the following the aeration step S113.

The number of pulses required is defined so as to ensure a sterilizationsecurity standard of 10⁻⁶ or lower (SAL<10⁻⁶). To achieve the standard,the operation of sterilization steps in a half cycle corresponding toone pulse needs to annihilate 10⁻⁶ or greater of indicator bacteria. Thepresent embodiment defines two pulses as a full cycle in all of thethree treatment modes.

The aeration step S113 is a step of decompressing the inside of thechamber 11 to a predetermined vacuum degree to remove the hydrogenperoxide and the ozone as the sterilization gas, and then injecting theair to reach a level of about the atmospheric pressure so as to dilutethe sterilization gas. In the present embodiment, the treatmentoperation in the aeration step S113 in the short mode differs from theother treatment modes.

First, the aeration step S113 in the case of the treatment mode that isthe short mode is described below. The time for the contact between thesterilization gas and the object to be sterilized is shorter for theshort mode than for the other modes. [0095] The aeration step S113 inthis case includes the following treatment step, for example, so as todecrease the treatment time.

The controller 61 first starts operating the vacuum pump 41 and opensthe eighth electromagnetic valve 77 to start the decompression of theinside of the chamber 11 immediately after the completion of the secondstate-keeping step S111 as early as possible. Simultaneously, thecontroller 61 opens the second electromagnetic valve 71, the thirdelectromagnetic valve 72, and the seventh electromagnetic valve 76, soas to discharge the remaining gas inside the evaporator 26 and thebuffer tank 34. The short mode keeps decompressing the inside of thechamber 11 until the internal pressure reaches 100 Pa, for example Thesterilization gas discharged passes through the first catalyst tank 42and the second catalyst tank 43, so as to lead the hydrogen peroxide tobe decomposed to be harmless water and oxygen and lead the ozone to bedecomposed to be harmless oxygen to be discharged to the outside of thesterilizer 100 with a concentration of a safety management value orlower. The controller 61 then closes the eighth electromagnetic valve 77when the pressure inside the chamber 11 reaches a predetermineddecompressed pressure.

The controller 61 then opens the ninth electromagnetic valve 78 and thetenth electromagnetic valve 79 to inject the air to the inside of thechamber 11 through the second filter 51. Simultaneously, the controller61 opens the second electromagnetic valve 71, the third electromagneticvalve 72, and the seventh electromagnetic valve 76 to inject the airalso to the inside of each of the evaporator 26 and the buffer tank 34.The injected air diffuses and dilutes the gas remaining inside thechamber 11, and removes the sterilization gas adhering to the object tobe sterilized or the inner surface of the chamber 11. The controller 61keeps injecting the air until the pressure inside the chamber 11 reachesabout 90 kPa that is about 90% of the atmospheric pressure, and thencloses the ninth electromagnetic valve 78 and the tenth electromagneticvalve 79.

The controller 61 repeats the decompression and the air injection asdescribed above for the prescribed number of times. In the short mode,the total repeated number of times may be three. When the time requiredfor the decompression is presumed to be about three minutes and the timerequired for the air injection is presumed to be about 0.5 minutes, theaeration step S113 is to take the time given by 3.5 minutes×threetimes=10.5 minutes. The controller 61 returns the pressure inside thechamber 11 to the atmospheric pressure by the air injection afterrepeating the decompression and the air injection for the prescribednumber of times, and finishes the aeration step S113. The controller 61ends the sterilization treatment after the aeration step S113.

Second, the aeration step S113 in the case of the treatment mode that isthe other modes other than the short mode is described below. The timefor the contact between the sterilization gas and the object to besterilized, and the amount of the hydrogen peroxide adhering to theobject to be sterilized or the amount of the hydrogen peroxide remaininginside the chamber 11 are greater for the other modes than the shortmode. The aeration step S113 in this case includes the followingtreatment step, for example.

The fundamental operations of the decompression and the air injectionare the same as those in the case in which the treatment mode is theshort mode. The pressure reaching upon the decompression, which is setto 100 Pa or lower in the short mode, is set to 50 Pa or lower in theother modes, for example, which is stricter than the case of the shortmode, since the object to be sterilized can have a duct part in theother modes.

The controller 61 keeps executing the decompression while injecting theair after the completion of the first decompression and air injection.In particular, the controller 61 starts operating the vacuum pump 41 andopens the eighth electromagnetic valve 77 to start the decompression,and then opens the ninth electromagnetic valve 78 and the tenthelectromagnetic valve 79 after a delay of about two seconds, forexample, so as to inject the air through the second filter 51. A timingof stopping the air injection at the time of injecting the air after thedecompression is presumed to be a point at which the pressure inside thechamber 11 is led to about 90 kPa or greater. A timing of stopping theair injection at the time of decompressing while injecting the air maybe set to a point at which the pressure inside the chamber 11 is led toabout 90 kPa or lower. The exhaustion during the air injection activatesthe flow of the air, so as to actively remove the sterilization gasadhering to the object to be sterilized or the inner surface of thechamber 11. Since the object to be sterilized is wrapped or covered withthe nonwoven fabric of fine mesh such as a sterilization bag or asterilization wrap particularly upon the normal sterilization treatment,the sterilization gas adhering to the nonwoven fabric can be effectivelyremoved. The time for decompressing while injecting the air is set toabout five minutes, for example.

The controller 61 further repeats the operations similar to thedecompression and the air injection executed first. The repeating numberof times in this case may be two, for example.

The aeration step S113 in this case takes about 15.5 minutes in total,in which the time required for the first decompression and air injectionis 3.5 minutes, the time required for decompressing while injecting theair is 5 minutes, and the time required for the second decompression andair injection is 3.5 minutes×2=7 minutes. The controller 61 then returnsthe pressure inside the chamber 11 to the atmospheric pressure by theair injection, and finishes the aeration step S113. The controller 61ends the sterilization treatment after the aeration step S113.

While the aeration step S113 repeats the decompression and the airinjection several times as described above, which is effective toeliminate the remaining sterilization gas, the treatment time isincreased as the repeating number is increased. When the decompressionand the air injection are repeated five times, for example, the time(five minutes) shorter than the time (six minutes) taken for repeatingtwo times (three minutes x two times) may be substituted for the nextrepeating time. This can discharge the sterilization gas remaininginside the chamber 11 more effectively, and further reduce the timerequired for the aeration step S113.

The treatment time taken for the sterilization treatment according tothe present embodiment described above in each treatment mode issubstantially as indicated in the table shown in FIG. 3. The operatorremoves the object to be sterilized from the chamber 11 after thecompletion of the series of the steps for the sterilization treatment.

The effects achieved by the sterilizing method and the sterilizer 100that can execute the sterilizing method according to the presentembodiment are described below.

The sterilizing method according to the present embodiment is tosterilize the object to be sterilized housed in the chamber 11. Thesterilizing method includes the first vapor injection step S104 ofinjecting, to the inside of the chamber 11, the vapor produced from thefirst aqueous solution of the hydrogen peroxide, and the ozone injectionstep S107 of injecting the ozone gas to the inside of the chamber 11after the first vapor injection step S104. The sterilizing methodfurther includes the second vapor injection step S109 of injecting, tothe inside of the chamber 11, the vapor produced from the pure water orthe vapor produced from the second aqueous solution of the hydrogenperoxide after the ozone injection step S107.

The sterilizer 100 according to the present embodiment includes thechamber 11 that houses the object to be sterilized, and the evaporator26 that communicates with the chamber 11 and evaporates the firstaqueous solution of the hydrogen peroxide, or the second aqueoussolution of the hydrogen peroxide or the pure water so as to be filledtherewith. The sterilizer 100 also includes the ozone generators 32 thatcommunicates with the chamber 11 and produces the ozone gas, and thecontroller 61 that controls the operation of injecting, to the inside ofthe chamber 11, the vapor produced by the evaporator 26 or the ozone gasproduced by the ozone generators 32. The controller 61 injects the ozonegas to the inside of the chamber 11 after injecting the vapor producedfrom the first aqueous solution, and injects the vapor produced from thepure water or the vapor produced from the second aqueous solution afterinjecting the ozone gas, so as to sterilize the object to be sterilized.

The present embodiment subjects the object to be sterilized to thesterilization treatment using the vapor of the first aqueous solutionand then to the sterilization treatment using the ozone gas. The presentembodiment further injects the vapor of the pure water or the secondaqueous solution after injecting the ozone gas to the inside of thechamber 11. This can improve the reactivity of the ozone gas, so as toincrease the sterilization efficiency of the sterilization treatmentmore than a case of executing the sterilization treatment only using theozone gas.

The sterilizing method and the sterilizer according to the presentembodiment thus can improve the sterilization efficiency in the entiresterilization treatment.

In the sterilizing method according to the present embodiment, theconcentration of the hydrogen peroxide contained in the second aqueoussolution may be lower than or equal to the concentration of the hydrogenperoxide contained in the first aqueous solution.

The injection of the vapor of the first aqueous solution in the presentembodiment is defined as a main sterilization treatment using thehydrogen peroxide as a material for the sterilization gas. The injectionof the vapor of the pure water or the second aqueous solution is definedas an auxiliary treatment for improving the sterilization efficiency ofthe sterilization treatment due to the injection of the ozone gas.Particularly when the vapor of the second aqueous solution is injectedin the second vapor injection step S109, the concentration of thehydrogen peroxide contained in the aqueous solution can be set to belower for the second aqueous solution than for the first aqueoussolution, or set to be equal to each other. This can decrease the usedamount of the hydrogen peroxide in the entire sterilization treatmentwhen the sterilizing method according to the present embodiment usesboth the first aqueous solution and the second aqueous solution. Inaddition, the amount of the hydrogen peroxide that may remain on thesurface of the object to be sterilized or inside the chamber 11 can bedecreased in proportion to the decrease in the used amount of thehydrogen peroxide.

In the sterilizing method according to the present embodiment, theconcentration of the hydrogen peroxide contained in the first aqueoussolution and the concentration of the hydrogen peroxide contained in thesecond aqueous solution may be determined in accordance with thepresence or absence of a duct part in the object to be sterilized or thematerial used for the object to be sterilized.

The present embodiment is illustrated above with the three treatmentmodes that differ from each other in the presence or absence of a ductpart in the object to be sterilized or the material used for the objectto be sterilized. For example, the object to be sterilized to which thesterilization treatment in the normal mode can be subjected is a thintube made of resin. The object to be sterilized to which thesterilization treatment in the long mode can be subjected is a thin tubemade of stainless steel. With regard to the comparison between the thintube of resin and the thin tube of stainless steel, the thin tube ofstainless steel is typically harder to sterilize than the thin tube ofresin. The reason for this is presumed that the reactivity between atransition element such as Fe, Mo, or Cr contained in stainless steeland the hydrogen peroxide is high, and the hydrogen peroxide is thusdecomposed in the middle of the treatment to impede the sufficientsupply of the hydrogen peroxide to the inside of the thin tube. Anotherreason for this is presumed that the thin tube of stainless steel hashigher thermal conductivity than the thin tube of resin, and is cooledunder a decompressed environment more quickly to easily cause watercondensation of the hydrogen peroxide inside the thin tube, whichimpedes the sufficient supply of the hydrogen peroxide to the inside ofthe thin tube.

When the thin tube of stainless steel is sterilized, for example, thepresent embodiment can deal with the above-described problem such thatthe concentration of the hydrogen peroxide contained in the secondaqueous solution is set to be higher than the concentration of thehydrogen peroxide contained in the second aqueous solution used in theother treatment modes. The concentration of the hydrogen peroxidecontained in the second aqueous solution in this case still does notexceed the concentration of the hydrogen peroxide contained in the firstaqueous solution. When the concentration of the hydrogen peroxidecontained in the second aqueous solution is equal to the concentrationof the hydrogen peroxide contained in the first aqueous solution, theinjected amount of the second aqueous solution can be decreased. Inother words, the present embodiment, when sterilizing the thin tube ofstainless steel, can particularly decrease the entire used amount of thehydrogen peroxide (the concentration of the hydrogen peroxide in thefirst aqueous solution and the second aqueous solution x the sum of theinjected amount of the hydrogen peroxide), as compared with conventionalsterilizing methods.

The sterilizing method according to the present embodiment may furtherinclude the outside air injection step of injecting the atmosphere ordry nitrogen gas to the inside of the chamber 11 after the second vaporinjection step.

The sterilizing method, when the object to be sterilized particularlyincludes a duct part, can push the hydrogen peroxide or the ozone gascongested in the middle of the duct part to the inside of the chamber 11due to the injection of the outside air, so as to further promote thesterilization. The injection of the atmosphere to the inside of thechamber 11 also equalizes the distribution of the concentration of thegas present inside the chamber 11, so as to ensure the uniformsterilization. The injection of the atmosphere to the inside of thechamber 11 further increases the internal pressure to lead the hydrogenperoxide in the vapor to be slightly condensed on the surface of theobject to be sterilized, so as to further improve the sterilizationeffect. Particularly when the outside air is the atmosphere, the costfor the raw material for the gas to be injected can be saved, and theconfiguration for injecting the air to the inside of the chamber 11 canbe simplified, so as to reduce the manufacturing costs for thesterilizer 100.

The sterilizing method according to the present embodiment may furtherinclude the state-keeping step of keeping the state of the inside of thechamber 11 for a predetermined period of time after the outside airinjection step. The state-keeping step herein corresponds to the secondstate-keeping step S111 as described above.

The sterilizing method thus can further promote the sterilization effectdue to the outside air injection step.

The sterilizing method according to the present embodiment may furtherinclude the first vapor preparation step S103 of injecting andevaporating the first aqueous solution in the evaporator 26 to lead theevaporator 26 to be filled therewith so as to produce the vapor to beinjected in the first vapor injection step S104. The sterilizing methodaccording to the present embodiment may further include the second vaporpreparation step S108 of injecting and evaporating the pure water or thesecond aqueous solution in the evaporator 26 to lead the evaporator 26to be filled therewith so as to produce the vapor to be injected in thesecond vapor injection step S108. The ozone gas in the ozone injectionstep S107 may be injected to the inside of the chamber 11 via the insideof the evaporator 26.

The sterilizing method thus can inject the vapor to the inside of thechamber 11 when the aqueous solution of the hydrogen peroxide isevaporated in the evaporator 26 and the pressure inside the evaporator26 is increased. The injection of the vapor can further enhance theuniform diffusion of the vapor inside the chamber 11. This also allowsthe hydrogen peroxide to easily enter the inside of the tube of theobject to be sterilized having the duct part. The sterilizing methodthus can further decrease the used amount of the hydrogen peroxide whilekeeping the sterilizing effect.

According to the sterilizing method, the ozone gas is injected to theinside of the chamber 11 through the inside of the evaporator 26, so asto use the ozone gas to push the hydrogen peroxide remaining in theevaporator 26 into the chamber 11 to further improve the sterilizationeffect. The introduction port provided in the chamber 11 can be used incommon as the port to which the hydrogen peroxide is introduced and theport to which the ozone gas is introduced, so as to simplify thecircumferential configuration of the chamber 11.

The sterilizing method according to the present embodiment may furtherinclude the ozone preparation step S106 of filling the inside of thebuffer tank 34 with the ozone gas before the ozone injection step S107.In the ozone injection step S107, the ozone gas filled in the buffertank 34 may be injected to the inside of the chamber 11.

The sterilizing method thus can inject the ozone gas to the inside ofthe chamber 11 when the pressure of the ozone gas in the buffer tank 34is increased. The injection of the ozone gas can further enhance theuniform diffusion of the ozone gas inside the chamber 11. This alsoallows the ozone to easily enter the inside of the tube of the object tobe sterilized having the duct part. The sterilizing method thus canfurther decrease the used amount of the ozone while keeping thesterilizing effect.

The sterilizing method according to the present embodiment may furtherinclude the aeration step S113 of repeating the air discharge from theinside of the chamber 11 and the injection of the atmosphere to theinside of the chamber 11 several times so as to lead the inside of thechamber 11 to be in a state of allowing the object to be sterilized tobe removed. The aeration step S113 may discharge the air inside thechamber 11 at least once while injecting the atmosphere to the inside ofthe chamber 11.

The sterilizing method can activate the flow of the air inside thechamber 11 by the air discharge in association with the air injection,so as to facilitate the removal of the sterilization gas adhering to theobject to be sterilized or the inner surface of the chamber 11. Further,the time required for the single operation of the air discharge inassociation with the air injection is shorter than the time required forthe single operation of the air injection after the decompression, so asto decrease the time necessary for the entire aeration step S113accordingly.

The sterilizing method and the sterilizer 100 according to the presentembodiment are further described below with reference to Example incomparison with two comparative examples.

FIG. 4 is a table showing various kinds of conditions for sterilizationtreatment tests executed for Comparative Example 1 and ComparativeExample 2, in addition to Example according to the present embodiment.FIG. 5 is a table showing results of each test executed under theconditions shown in FIG. 4. FIG. 5 shows a negative rate for each test.The column on the left side of the negative rate indicates the number ofbiological indicators used as described below that show the negativerate. The respective tests were executed for three days, and therespective values in parentheses in the column of the negative rateindicate the test results obtained in each day.

The respective tests use strip-type biological indicators (BIs) suitablefor mainly evaluating the surface sterilization for the object to besterilized for ease of comparison of the sterilization effect. Inparticular, the BI used in each test is HMV-091-type available from APEX(bacterium number: ATCC12980, 21×10⁶ cfu/disc, D value: 1.0 min). Theterm “D value” refers to a time necessary for annihilating 90% of testbacteria and decreasing a survival rate to one tenth. Three to five BIsare exposed per test. Since the BIs used are not a thin tube having aduct part, the step of the air injection corresponding to the outsideair injection step S508 in the present embodiment is omitted so as tofacilitate the comparison particularly between Example and ComparativeExample 1.

A chamber used in each test is presumed to have the same structure underthe same conditions as the chamber 11 described above. In particular,the capacity of the chamber 11 is 100 L, and is preliminarily heated to50° C. Only the BIs are preliminarily housed in the chamber 11. Theother test conditions are as shown in FIG. 4. The injected amount of theaqueous solution of the hydrogen peroxide injected in the first time(referred to below as a “first aqueous solution” in all the tests forillustration purposes) is set to be the same in all the tests for easeof comparison.

FIG. 6 is a graph showing a change in pressure inside the chamber 11 inComparative Example 1. The sterilization step in Comparative Example 1simulates the sterilizing method disclosed in Patent Literature 1. InComparative Example 1, the vapor of the first aqueous solution isinjected to the inside of the chamber 11 at a timing T11 after thedecompression, and is kept during a period H11. The ozone gas is theninjected to the inside of the chamber 11 at a timing T12, and is keptduring a period H12. The aeration step is finally executed at a timingT13.

FIG. 7 is a graph showing a change in pressure inside the chamber 11 inComparative Example 2. The sterilization step in Comparative Example 2does not execute the injection of the ozone gas. In Comparative Example2, the vapor of the first aqueous solution is injected to the inside ofthe chamber 11 at a timing T21 after the decompression, and is keptduring a period H21. The air is then injected to the inside of thechamber 11 at a timing T22. The aeration step is finally executed.

FIG. 8 is a graph showing a change in pressure inside the chamber 11 inExample. In Example, the vapor of the first aqueous solution is injectedto the inside of the chamber 11 at a timing T1 after the decompression(the first vapor injection step S104), and is kept during a period H1(the first state-keeping step S105). The ozone gas is then injected tothe inside of the chamber 11 at a timing T2 (the ozone injection stepS107). The vapor is continuously injected to the inside of the chamberat a timing T3 and a timing T4 (the second vapor injection step S109),and is kept during a period H2 (the second state-keeping step S111).While the sterilization step is illustrated above with the case ofinjecting the vapor of the second aqueous solution in the second vaporinjection step S109, Example uses the vapor of the pure water as anexample of not having the sterilization effect when assumed to be usedindependently. The aeration step is finally executed at a timing TS.

The results of the respective tests revealed that, as shown in FIG. 5,upon the comparison of the negative rate in each test, Example has thehigher negative rate than Comparative Example 1 or Comparative Example2, showing that Example has the higher sterilization effect thanComparative Example 1 or Comparative Example 2.

Second Embodiment

FIG. 9 is a flowchart showing a process of a sterilizing methodaccording to a second embodiment. As in the case of the aboveembodiment, the object to be sterilized is housed in the chamber 11 ofthe sterilizer 100 in the state of being put in a sterilization bag orwrapped with a sterilization wrap upon the execution of thesterilization treatment. The first embodiment is illustrated above withthe case of subsequently proceeding to the first decompression step S102after the completion of the treatment mode selection step S101. Thepresent embodiment may further inject the ozone gas to the inside of thechamber 11 between the treatment mode selection step S101 and the firstdecompression step S102. The step of injection the ozone gas executedbetween the two steps is referred to as a preliminary ozone injectionstep so as to distinguish the injection of the ozone gas in the ozoneinjection step S107.

FIG. 10 is a graph showing a change in pressure inside the chamber 11according to the present embodiment. The pressure inside the chamber 11is first decompressed to 100 Pa, for example, so as to remove excessiveair from the inside of the chamber 11 (a preliminary decompression stepS201). FIG. 10 indicates a period in which the preliminary decompressionstep S201 is executed by H31. After the preliminary decompression stepS201, the ozone gas may be injected to the inside of the chamber 11 at atiming T31 (a preliminary ozone injection step S202), and kept during aperiod H32. The control made by the controller 61 upon the injection ofthe ozone gas is similar to the control in the ozone injection step S107as described in the first embodiment. A preliminary ozone preparationstep similar to the ozone preparation step S106 may be executed beforethe preliminary ozone injection step S202. The inside of the chamber 11is then decompressed during a period H33 (the first decompression stepS102). The inside of the chamber 11 may be kept during a period H34after the first decompression step S102. Next, the vapor of the firstaqueous solution is injected to the inside of the chamber 11 at a timingT32 (the first vapor injection step S104), and is kept during a periodH35 (the first state-keeping step S105). Next, the ozone gas is injectedto the inside of the chamber 11 at a timing T33 (the ozone injectionstep S107). The vapor of the pure water or the second aqueous solutionis then injected to the inside of the chamber 11 at a timing T34 (thesecond vapor injection step S109), and the atmosphere is subsequentlyinjected at a timing T35 (the outside air injection step S110). Theinside of the chamber 11 is kept during a period H36 (the secondstate-keeping step S111). FIG. 10 illustrates the case of repeating thesterilization step for two pulses. The controller 61 determines that thesterilization step needs to be repeated (YES) in the determination stepS112, and leads the sterilization step to be repeatedly executed for thesecond pulse. After the completion of the sterilization step at thesecond pulse, the controller 61 determines that no more repetition isrequired (NO) in the determination step S112, and then executes theaeration step S113.

As described above, the sterilizing method according to the presentembodiment may include the preliminary ozone injection step S202 ofinjecting the ozone gas to the inside of the chamber 11 before the firstvapor injection step S104.

Since ozone causing a strong oxidation action is easy to react with anysubstances, the ozone gas injected in the ozone injection step S107 mayadhere to the nonwoven fabric such as a sterilization wrap to decomposeit before reaching the object to be sterilized. The sterilizing methodaccording to the present embodiment can preliminarily apply the ozonegas to penetrate the nonwoven fabric in the preliminary ozone injectionstep S202. This leads the oxidation action to be saturated on thesurface of the nonwoven fabric, and prevents the ozone gas injected inthe ozone injection step S107 from further reacting with the nonwovenfabric, so as to easily reach the object to be sterilized, avoiding areduction in the sterilization effect accordingly.

It should be understood that the present disclosure includes variousembodiments not described herein.

REFERENCE SIGNS LIST

11 CHAMBER

26 EVAPORATOR

32 OZONE GENERATOR

61 CONTROLLER

100 STERILIZER

1. A sterilizing method for sterilizing a sterilization object housed ina chamber, the method comprising: a first vapor injection step ofinjecting vapor produced from a first aqueous solution of hydrogenperoxide to an inside of the chamber; an ozone injection step ofinjecting ozone gas to the inside of the chamber after the first vaporinjection step; and a second vapor injection step of injecting vaporproduced from pure water or vapor produced from a second aqueoussolution of hydrogen peroxide to the inside of the chamber after theozone injection step.
 2. The sterilizing method according to claim 1,wherein a concentration of the hydrogen peroxide contained in the secondaqueous solution is lower than or equal to a concentration of thehydrogen peroxide contained in the first aqueous solution.
 3. Thesterilizing method according to claim 1, wherein a concentration of thehydrogen peroxide contained in the first aqueous solution and aconcentration of the hydrogen peroxide contained in the second aqueoussolution are determined in accordance with a presence or absence of aduct part in the sterilization object or a material used for thesterilization object.
 4. The sterilizing method according to claim 1,further comprising an outside air injection step of injecting anatmosphere or dry nitrogen gas to the inside of the chamber after thesecond vapor injection step.
 5. The sterilizing method according toclaim 4, further comprising a state-keeping step of keeping a state ofthe inside of the chamber for a predetermined period of time after theoutside air injection step.
 6. The sterilizing method according to claim1, further comprising: a first vapor preparation step of injecting andevaporating the first aqueous solution in an evaporator to lead theevaporator to be filled therewith so as to produce the vapor to beinjected in the first vapor injection step; and a second vaporpreparation step of injecting and evaporating the pure water or thesecond aqueous solution in the evaporator to lead the evaporator to befilled therewith so as to produce the vapor to be injected in the secondvapor injection step, wherein the ozone gas in the ozone injection stepis injected to the inside of the chamber via an inside of theevaporator.
 7. The sterilizing method according to claim 1, furthercomprising an ozone preparation step of filling an inside of a buffertank with the ozone gas before the ozone injection step, wherein theozone gas filled in the inside of the buffer tank in the ozone injectionstep is injected to the inside of the chamber.
 8. The sterilizing methodaccording to claim 1, further comprising a preliminary ozone injectionstep of injecting the ozone gas to the inside of the chamber before thefirst vapor injection step.
 9. The sterilizing method according to claim1, further comprising an aeration step of repeating an air dischargefrom the inside of the chamber 11 and an air injection to the inside ofthe chamber 11 several times so as to lead the inside of the chamber tobe in a state of allowing the sterilization object to be removed,wherein the aeration step executes the air discharge at least once inassociation with the air injection to the inside of the chamber.
 10. Asterilizer comprising: a chamber configured to house a sterilizationobject; an evaporator configured to communicate with the chamber andevaporate a first aqueous solution of hydrogen peroxide, or a secondaqueous solution of hydrogen peroxide or pure water so as to be filledtherewith; an ozone generator configured to communicate with the chamberand produce ozone gas; and a controller configured to control anoperation of injecting, to an inside of the chamber, vapor produced bythe evaporator or the ozone gas produced by the ozone generator, whereinthe controller injects the ozone gas to the inside of the chamber afterinjecting the vapor produced from the first aqueous solution, andinjects the vapor produced from the pure water or the second aqueoussolution to the inside of the chamber after injecting the ozone gas soas to sterilize the sterilization object.
 11. The sterilizer accordingto claim 10, wherein: the ozone generator communicates with the chambervia the evaporator; and the ozone gas produced by the ozone generator isinjected to the inside of the chamber via an inside of the evaporator.12. The sterilizer according to claim 10, further comprising a buffertank arranged between the ozone generator and the evaporator and causedto be filled with the ozone gas produced by the ozone generator beforethe ozone gas is supplied to the evaporator, wherein the controllerinjects the ozone gas filled in the buffer tank to the inside of thechamber.